Introduction

The U-Loop technology is a process occurring in nature and industrialized by Unibio. The process is described in the below video.

The Concept

The concept underlying Unibio’s U-Loop technology is simple: natural gas (methane) can be converted into a highly concentrated protein product which can be used in feed for animals (see diagram below).

The product has been branded UniProtein® and can substitute an increasingly scarce resource – fishmeal. On top of that, when the U-Loop technology is employed in production plants, CO₂ emissions are reduced by 52% as compared to when natural gas is burnt for producing electricity.

The U-Loop technology is patented under process patent No PA199900690. Unibio’s patent for U-shape and/or Nozzle-U-Loop fermentor and method of carrying out a fermentation process has been approved in Canada, Mexico and the US, and the patent for U-shape and/or Nozzle-U-Loop fermentor and method of fermentation has been approved in Mexico and is pending in Brazil, Canada, the EU and the US.

Technical Explanation

The continuous fermentation is operated with 2-3% biomass (dry matter) and a dilution rate of 0.20-0.25 h-1. The biomass of the harvest is concentrated to over 22% by centrifugation and then to approximately 30% by UHT at 70°C. In the process, the biomass is inactivated, and the cell undergoes lysis so that the protein becomes more accessible. Finally, the UHT-treated biomass is dried in a spray dryer with an integrated fluid bed. This gives a non-dusty agglomerated product.

In order to minimize the use of process water and to minimize the amount of waste water, process water from the centrifuges and ultrafiltration is returned to the fermentor after a short heat treatment.

Input Requirements

Natural gas is the main raw material used in UniProtein® production, and it is used as the carbon and energy source. Technically pure oxygen is used for an oxygenation fermentation process, and ammonia is used as the nitrogen source. In addition to these substrates, the UniProtein® culture requires water, phosphate and several minerals including magnesium, calcium, potassium, iron, copper, zinc, manganese, nickel, cobalt and molybdenum. Sodium hydroxide and sulphuric acid are used for pH regulation. All chemicals are of food-grade quality. Phosphate is supplied as phosphoric acid, the minerals as sulphates, chlorides or nitrates. The pH is regulated to 6.5±0.3, and the temperature is kept at 45°C±2°C.

The fermentor and its design (see below) are the most important aspects of the U-Loop production process. In traditional stirred fermentors there are problems with achieving sufficiently small bubbles (large surface area of the gas), and there is a large energy waste due to inefficient stirring of the bulk liquid. Furthermore, there are problems with cooling when upscaling.

UniProtein® is produced in a continuous fermentation process. A U-Loop fermentor with static mixers is used. The U-Loop fermentor gives a high utilization of the gases, which are carried through the loop by the liquid flow in almost plug-flow mode. The gases are introduced at the start of the loop and stay in well-mixed contact with the liquid until they are separated in the headspace at the end of the loop.

The fermentor that is to be used in UniProtein® production is based on a patented U-Loop design developed in cooperation with DTU. The Nozzle U-Loop design makes it possible to obtain an optimal fermentation process with the highest possible product output (larger surface area) in the shortest possible time, i.e. 4kg/m3/h against 1.8kg/m3/h for conventional fermentors. There is about 30% energy saving in the Nozzle U-Loop fermentor. In addition, there is no need for mechanical stirring in the U-Loop fermentor.